Inkjet Nozzle Device With Cantilevered Actuating Arm

ABSTRACT

A nozzle device for an inkjet printer includes a support structure defining an ink chamber connected to a source of ink; a nozzle chamber for receiving ink from the ink chamber; a nozzle opening through which ink in the nozzle chamber is ejected; and an elongate actuating arm cantilevered relative to the support structure and terminating in a movable free end within the nozzle chamber, the actuating arm comprising an active portion connected electrically to a current source and a passive portion electrically isolated from the current source. The passive portion is mechanically coupled to the active portion via at least one separating element, whereby differential expansion between the active and passive portions causes the actuating arm to bend and the free end of the actuating arm to move within the nozzle chamber to eject ink therein through the nozzle opening. The elongate actuating arm divides the nozzle chamber from the ink chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No.11/730,786 filed Apr. 4, 2007, which is a Continuation of U.S.application Ser. No. 11/339,493 filed on Jan. 26, 2006, now issued U.S.Pat. No. 7,210,666, which is a Continuation of U.S. application Ser. No.11/165,198, filed on Jun. 24, 2005, now issued as U.S. Pat. No.7,128,093, which is a Continuation of U.S. application Ser. No.10/949,346 filed on Sep. 27, 2004, now issued as U.S. Pat. No.6,969,142, which is a Continuation of U.S. application Ser. No.10/636,273 filed on Aug. 8, 2003, now issued as U.S. Pat. No. 6,802,587,which is a Continuation of U.S. application Ser. No. 09/575,175 filed onMay 23, 2000, now issued as U.S. Pat. No. 6,629,745, all of which areherein incorporated by reference.

CO-PENDING APPLICATIONS

Various methods, systems and apparatus relating to the present inventionare disclosed in the following co-pending applications/granted patentsfiled by the applicant or assignee of the present inventionsimultaneously with U.S. Pat. No. 6,629,745:

6,428,133 6,526,658 6,315,399 6,338,548 6,540,319 6,328,431 6,328,4256,991,320 6,383,833 6,464,332 6,390,591 7,018,016 6,328,417 09/575,1977,079,712 6,975,429 6,825,945 7,330,974 6,813,039 6,987,506 7,038,7976,980,318 6,816,274 7,350,236 6,681,045 6,728,000 7,173,722 7,088,45909/575,181 7,068,382 7,062,651 6,789,194 6,789,191 6,644,642 6,502,6146,622,999 6,669,385 6,549,935 6,987,573 6,727,996 6,591,884 6,439,7066,760,119 7,295,332 6,290,349 6,428,155 6,785,016 6,870,966 6,822,6396,737,591 7,055,739 7,233,320 6,830,196 6,832,717 6,957,768 7,259,8897,456,820 7,170,499 7,106,888 7,123,239 6,409,323 6,281,912 6,604,8106,318,920 6,488,422 6,795,215 7,154,638 6,859,289 6,924,907 6,416,1606,238,043 6,958,826 6,812,972 6,553,459 6,967,741 6,956,669 6,903,7666,804,026The disclosures of these co-pending applications are incorporated hereinby cross-reference.

FIELD OF THE INVENTION

This invention relates to a method of detecting and, if appropriate,remedying a fault in a micro-electromechanical device. The invention hasapplication in ink ejection nozzles of the type that are fabricated byintegrating the technologies applicable to micro electro-mechanicalsystems (MEMS) and complementary metal-oxide semiconductor (CMOS)integrated circuits, and the invention is hereinafter described in thecontext of that application. However, it will be understood that theinvention does have broader application, to the remedying of faultswithin various types of MEM devices.

BACKGROUND OF THE INVENTION

A high speed pagewidth inkjet printer has recently been developed by thepresent Applicant. This typically employs in the order of 51200 inkjetnozzles to print on A4 size paper to provide photographic quality imageprinting at 1600 dpi. In order to achieve this nozzle density, thenozzles are fabricated by integrating MEMS-CMOS technology.

A difficulty that flows from the fabrication of such a printer is thatthere is no convenient way of ensuring that all nozzles that extendacross the printhead or, indeed, that are located on a given chip willperform identically, and this problem is exacerbated when chips that areobtained from different wafers may need to be assembled into a givenprinthead. Also, having fabricated a complete printhead from a pluralityof chips, it is difficult to determine the energy level required foractuating individual nozzles, to evaluate the continuing performance ofa given nozzle and to detect for any fault in an individual nozzle.

SUMMARY OF THE INVENTION

According to one aspect of the disclosure, a nozzle device for an inkjetprinter includes a support structure defining an ink chamber connectedto a source of ink; a nozzle chamber for receiving ink from the inkchamber; a nozzle opening through which ink in the nozzle chamber isejected; and an elongate actuating arm cantilevered relative to thesupport structure and terminating in a movable free end within thenozzle chamber, the actuating arm comprising an active portion connectedelectrically to a current source and a passive portion electricallyisolated from the current source. The passive portion is mechanicallycoupled to the active portion via at least one separating element,whereby differential expansion between the active and passive portionscauses the actuating arm to bend and the free end of the actuating armto move within the nozzle chamber to eject ink therein through thenozzle opening. The elongate actuating arm divides the nozzle chamberfrom the ink chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:—

FIG. 1: shows a highly magnified cross-sectional elevation view of aportion of the inkjet nozzle,

FIG. 2: shows a plan view of the inkjet nozzle of FIG. 1,

FIG. 3: shows a perspective view of an outer portion of an actuating armand an ink ejecting paddle or of the inkjet nozzle, the actuating armand paddle being illustrated independently of other elements of thenozzle,

FIG. 4: shows an arrangement similar to that of FIG. 3 but in respect ofan inner portion of the actuating arm,

FIG. 5: shows an arrangement similar to that of FIGS. 3 and 4 but inrespect of the complete actuating arm incorporating the outer and innerportions shown in FIGS. 3 and 4,

FIG. 6: shows a detailed portion of a movement sensor arrangement thatis shown encircled in FIG. 5,

FIG. 7: shows a sectional elevation view of the nozzle of FIG. 1 butprior to charging with ink,

FIG. 8: shows a sectional elevation view of the nozzle of FIG. 7 butwith the actuating arm and paddle actuated to a test position,

FIG. 9: shows ink ejection from the nozzle when actuated under a faultclearing operation,

FIG. 10: shows a blocked condition of the nozzle when the actuating armand paddle are actuated to an extent that normally would be sufficientto eject ink from the nozzle,

FIG. 11: shows a schematic representation of a portion of an electricalcircuit that is embodied within the nozzle,

FIG. 12: shows an excitation-time diagram applicable to normal (inkejecting) actuation of the nozzle actuating arm,

FIG. 13: shows an excitation-time diagram applicable to test actuationof the nozzle actuating arm,

FIG. 14: shows comparative displacement-time curves applicable to theexcitation-time diagrams shown in FIGS. 12 and 13,

FIG. 15: shows an excitation-time diagram applicable to a faultdetection procedure,

FIG. 16: shows a temperature-time diagram that is applicable to thenozzle actuating arm and which corresponds with the excitation-timediagram of FIG. 15, and

FIG. 17: shows a deflection-time diagram that is applicable to thenozzle actuating arm and which corresponds with theexcitation/heating-time diagrams of FIGS. 15 and 16.

DETAILED DESCRIPTION OF THE INVENTION

The fault detection method of the invention preferably is employed inrelation to an MEM device in the form of a liquid ejector and mostpreferably in the form of an ink ejection nozzle that is operable toeject an ink droplet upon actuation of the actuating arm. In this latterpreferred form of the invention, the second end of the actuating armpreferably is coupled to an integrally formed paddle which is employedto displace ink from a chamber into which the actuating arm extends.

The actuating arm most preferably is formed from two similarly shapedarm portions which are interconnected in interlapping relationship. Inthis embodiment of the invention, a first of the arm portions isconnected to a current supply and is arranged in use to be heated by thecurrent pulse or pulses having the duration t_(p). However, the secondarm portion functions to restrain linear expansion of the actuating armas a complete unit and heat induced elongation of the first arm portioncauses bending to occur along the length of the actuating arm. Thus, theactuating arm is effectively caused to pivot with respect to the supportstructure with heating and cooling of the first portion of the actuatingarm.

As illustrated with approximately 3000× magnification in FIG. 1 andother relevant drawing figures, a single inkjet nozzle device is shownas a portion of a chip that is fabricated by integrating MEMS and CMOStechnologies. The complete nozzle device includes a support structurehaving a silicon substrate 20, a metal oxide semiconductor layer 21, apassivation layer 22, and a non-corrosive dielectriccoating/chamber-defining layer 23.

The nozzle device incorporates an ink chamber 24 which is connected to asource (not shown) of ink and, located above the chamber, and a nozzlechamber 25. A nozzle opening 26 is provided in the chamber-defininglayer 23 to permit displacement of ink droplets toward paper or othermedium (not shown) onto which ink is to be deposited. A paddle 27 islocated between the two chambers 24 and 25 and, when in its quiescentposition, as indicated in FIGS. 1 and 7, the paddle 27 effectivelydivides the two chambers 24 and 25.

The paddle 27 is coupled to an actuating arm 28 by a paddle extension 29and a bridging portion 30 of the dielectric coating 23.

The actuating arm 28 is formed (i.e. deposited during fabrication of thedevice) to be pivotable with respect to the support structure orsubstrate 20. That is, the actuating arm has a first end that is coupledto the support structure and a second end 38 that is movable outwardlywith respect to the support structure. The actuating arm 28 comprisesouter and inner arm portions 31 and 32. The outer arm portion 31 isillustrated in detail and in isolation from other components of thenozzle device in the perspective view shown in FIG. 3. The inner armportion 32 is illustrated in a similar way in FIG. 4. The completeactuating arm 28 is illustrated in perspective in FIG. 5, as well as inFIGS. 1, 7, 8, 9 and 10.

The inner portion 32 of the actuating arm 28 is formed from atitanium-aluminium-nitride (TiAL)N deposit during formation of thenozzle device and it is connected electrically to a current source 33,as illustrated schematically in FIG. 11, within the CMOS structure. Theelectrical connection is made to end terminals 34 and 35, andapplication of a pulsed excitation (drive) voltage to the terminalsresults in pulsed current flow through the inner portion only of theactuating arm 28. The current flow causes rapid resistance heatingwithin the inner portion 32 of the actuating arm and consequentialmomentary elongation of that portion of the arm.

The outer arm portion 31 of the actuating arm 28 is mechanically coupledto but electrically isolated from the inner arm portion 32 by posts 36.No current-induced heating occurs within the outer arm portion 31 and,as a consequence, voltage induced current flow through the inner armportion 32 causes momentary bending of the complete actuating arm 28 inthe manner indicated in FIGS. 8, 9 and 10 of the drawings. This bendingof the actuating arm 28 is equivalent to pivotal movement of the armwith respect to the substrate 20 and it results in displacement of thepaddle 27 within the chambers 24 and 25.

An integrated movement sensor is provided within the device in order todetermine the degree or rate of pivotal movement of the actuating arm 28and in order to permit fault detection in the device.

The movement sensor comprises a moving contact element 37 that is formedintegrally with the inner portion 32 of the actuating arm 28 and whichis electrically active when current is passing through the inner portionof the actuating arm. The moving contact element 37 is positionedadjacent the second end 38 of the actuating arm and, thus, with avoltage V applied to the end terminals 34 and 35, the moving contactelement will be at a potential of approximately V/2. The movement sensoralso comprises a fixed contact element 39 which is formed integrallywith the CMOS layer 22 and which is positioned to be contacted by themoving contact element 37 when the actuating arm 28 pivots upwardly to apredetermined extent. The fixed contact element is connectedelectrically to amplifier elements 40 and to a microprocessorarrangement 41, both of which are shown in FIG. 11 and the componentelements of which are embodied within the CMOS layer 22 of the device.

When the actuator arm 28 and, hence, the paddle 27 are in the quiescentposition, as shown in FIGS. 1 and 7, no contact is made between themoving and fixed contact elements 37 and 39. At the other extreme, whenexcess movement of the actuator arm and the paddle occurs, as indicatedin FIGS. 8 and 9, contact is made between the moving and fixed contactelements 37 and 39. When the actuator arm 28 and the paddle 27 areactuated to a normal extent sufficient to expel ink from the nozzle, nocontact is made between the moving and fixed contact elements. That is,with normal ejection of the ink from the chamber 25, the actuator arm 28and the paddle 27 are moved to a position partway between the positionsthat are illustrated in FIGS. 7 and 8. This (intermediate) position isindicated in FIG. 10, although as a consequence of a blocked nozzlerather than during normal ejection of ink from the nozzle.

FIG. 12 shows an excitation-time diagram that is applicable to effectingactuation of the actuator arm 28 and the paddle 27 from a quiescent to alower-than-normal ink ejecting position. The displacement of the paddle27 resulting from the excitation of FIG. 12 is indicated by the lowergraph 42 in FIG. 14, and it can be seen that the maximum extent ofdisplacement is less than the optimum level that is shown by thedisplacement line 43.

FIG. 13 shows an expanded excitation-time diagram that is applicable toeffecting actuation of the actuator arm 28 and the paddle 27 to anexcessive extent, such as is indicated in FIGS. 8 and 9. Thedisplacement of the paddle 27 resulting from the excitation of FIG. 13is indicated by the upper graph 44 in FIG. 14, from which it can be seenthat the maximum displacement level is greater than the optimum levelindicated by the displacement line 43.

FIGS. 15, 16 and 17 shows plots of excitation voltage, actuator armtemperature and paddle deflection against time for successivelyincreasing durations of excitation applied to the actuating arm 28.

The device can be calibrated to determine an optimal level ofdisplacement of the actuator arm by applying a series of current pulsesof increasing duration as shown in FIG. 15. From these current pulses,the relationship between the current pulse width and displacement can bedetermined, which relationship can also determine the minimum currentpulse to achieve correct operation, as indicated by the test level linein FIG. 17. By correctly calibrating the device, minimum energy can beapplied to the device while still achieving correct operation.The plots shown in FIGS. 15, 16 and 17 also have relevance to faultdetection in the nozzle device.

When detecting for a fault condition in the nozzle device or in eachdevice in an array of the nozzle devices, a series of current pulses ofsuccessively increasing duration t_(p) are induced to flow that theactuating arm 28 over a time period t. The duration t_(p) is controlledto increase in the manner indicated graphically in FIG. 15.

Each current pulse induces momentary heating in the actuating arm and aconsequential temperature rise, followed by a temperature drop onexpiration of the pulse duration. As indicated in FIG. 16, thetemperature rises to successively higher levels with the increasingpulse durations as shown in FIG. 15.

As a result, as indicated in FIG. 17, under normal circumstances theactuator arm 28 will move (i.e. pivot) to successively increasingdegrees, some of which will be below that required to cause contact tobe made between the moving and fixed contact elements 37 and 39 andothers of which will be above that required to cause contact to be madebetween the moving and fixed contact elements. This is indicated by the“test level” line shown in FIG. 17. However, if a blockage occurs in anozzle device, as indicated in FIG. 10, the paddle 27 and, as aconsequence, the actuator arm 28 will be restrained from moving to thenormal full extent that would be required to eject ink from the nozzle.As a consequence, the normal full actuator arm movement will not occurand contact will not be made between the moving and fixed contactelements 37 and 39.

If such contact is not made with passage of current pulses of thepredetermined duration t_(p) through the actuating arm, it might beconcluded that a blockage has occurred within the nozzle device. Thismight then be remedied by passing a further current pulse through theactuating arm 28, with the further pulse having an energy levelsignificantly greater than that which would normally be passed throughthe actuating arm. If this serves to remove the blockage ink ejection asindicated in FIG. 9 will occur.

As an alternative, simpler, procedure toward fault detection, a singlecurrent pulse as indicated in FIG. 12 may be induced to flow through theactuator arm and detection be made simply for sufficient movement of theactuating arm to cause contact to be made between the fixed and movingcontact elements.

Variations and modifications may be made in respect of the device asdescribed above as a preferred embodiment of the invention withoutdeparting from the scope of the appended claims.

1. A nozzle device for an inkjet printer, the nozzle device comprising:a support structure defining an ink chamber connected to a source ofink; a nozzle chamber for receiving ink from the ink chamber; a nozzleopening through which ink in the nozzle chamber is ejected; and anelongate actuating arm cantilevered relative to the support structureand terminating in a movable free end within the nozzle chamber, theactuating arm comprising an active portion connected electrically to acurrent source and a passive portion electrically isolated from thecurrent source, wherein the passive portion is mechanically coupled tothe active portion via at least one separating element, wherebydifferential expansion between the active and passive portions causesthe actuating arm to bend and the free end of the actuating arm to movewithin the nozzle chamber to eject ink therein through the nozzleopening, and the elongate actuating arm divides the nozzle chamber fromthe ink chamber.
 2. A nozzle device as claimed in claim 1, furthercomprising a movement sensor for determining the degree or rate ofpivotal movement of the actuating arm.
 3. A nozzle device as claimed inclaim 2, wherein the movement sensor comprises a movable contact elementextending from the active portion, and a fixed contact element extendingfrom the support structure in a position, the movable contact elementadapted to contact the fixed contact element upon activation of thecurrent source.
 4. A nozzle device as claimed in claim 3, wherein theactive portion is substantially U-shaped and the movable contact elementis located proximal to the centre of the active portion.
 5. A nozzledevice as claimed in claim 4, wherein the free ends of the activeportion define a pair of enlarged contacts.
 6. A nozzle device asclaimed in claim 1, wherein the nozzle chamber comprises: a staticportion extending from the support structure, defining the nozzleopening; and a movable wall portion mounted to the cantileveredactuating arm between the fixed and free ends of the actuating arm.
 7. Anozzle device as claimed in claim 6, wherein the static formationextends from the support structure towards the actuating arm at alocation proximal to the movable wall portion, the static formationimpeding the escape of ink from within the nozzle chamber duringactuation of the actuating arm, whereby an ink meniscus is formedbetween the static formation and the actuating arm.
 8. A nozzle deviceas claimed in claim 7, wherein the static formation defines a bent freeend which bends away from the nozzle chamber.
 9. A nozzle device asclaimed in claim 8, wherein the support structure defines a well locatedin alignment with the bent free end, the well collecting any escaped inkfrom the nozzle chamber.
 10. A nozzle device as claimed in claim 1,wherein the free end of the actuating arm comprises a paddle spanningthe nozzle chamber.